Field of the Invention
The invention relates to a circuit arrangement and a method for compensating for a signal damping while transmitting transmission signals of a wireless mobile device. The invention also relates optionally to the compensation for a signal damping while transmitting reception signals of the wireless mobile device.
It is known, e.g. from WO 2007/118694 A1, to couple a mobile telephone wirelessly via an antenna structure to devices of a motor vehicle, in particular to an external antenna of the motor vehicle. The transmission and reception signals of the wireless mobile device are transmitted and received via the external antenna. The quality of the radio link can be significantly increased as a result.
The invention relates, in particular, to a circuit arrangement for transmitting transmission and reception signals of a wireless mobile device (e.g. a mobile telephone, a smartphone or an emergency transmitter), which are used in motor vehicles. However, a circuit arrangement which, in particular, has a wireless signal coupling device as essentially described in WO 2007/118694 A1 can also be used in a stationary manner, e.g. in buildings in order to transmit signals e.g. via an external antenna on the building in a mobile network or via a mobile radio link and thus improve the transmission quality compared with the exclusive use of the antenna of the wireless mobile device.
A circuit arrangement with the wireless signal coupling device already mentioned is the main application of the invention. A coupling device of this type simplifies the handling of wireless mobile devices, since no line connection (i.e., in particular, a cable connection) to the wireless mobile device needs to be established in order to be able to operate it in combination with the circuit arrangement. However, also in other circuit arrangements for transmitting transmission signals from wireless mobile devices which are used in addition to the wireless mobile device, an additional signal damping which is caused by the circuit arrangement and optionally by the additional components may occur due to the circuit arrangement or additional components optionally connected to it. In particular, high-frequency lines for transmitting the signals within the circuit arrangement, frequency filters, frequency separating filters, detectors contribute to the additional signal damping.
As long as the additional signal damping is temporally constant, it can be compensated for in a simple manner by means of a signal amplifier with a corresponding, constant amplification factor which re-amplifies the signals and thus compensates for the damping. In contrast to repeaters, also referred to as translators, it is not desirable to increase the signal level above the level which the signal has directly on the transmit antenna of the wireless mobile device (in relation to the transmission signals of the device) or directly on the external antenna (in relation to the signals received from the mobile network). This would be disadvantageous as it would interfere with the alignment of the transmitted and received power that takes place between the wireless mobile device and a mobile station of the mobile network or the mobile link. Either the alignment would be hindered or adversely affected or an alignment of these powers or signal levels would have to be carried out by the circuit arrangement itself through communication with the wireless mobile device and the mobile station. This would incur a high circuitry cost.
In the aforementioned type of circuit arrangements, which, in combination with the respective wireless mobile device, cause a different additional signal damping depending on the state of the combination, the objective of the most exact possible compensation of the additional signal damping is not achievable with a constant signal amplification that is identical for each possible state. It is conceivable to determine the additional signal damping in each of the possible states of the combination and to set the signal amplification accordingly. However, since wireless mobile devices, as mentioned, transmit their transmission signals with variable transmitted power, depending on the result of the alignment with the mobile station, the determination of the additional signal damping is not possible or in turn requires an alignment with the wireless mobile device. For example, the wireless mobile device would have to transmit a transmission signal with a predefined or known transmitted power in a time period that is known to the circuit arrangement. The problem here is also that the state of the coupling between the wireless mobile device and the circuit arrangement may change in an unforeseen and unknown manner, resulting in a change in the additional signal damping.
For example, the wireless mobile device as described in WO 2007/118694 A1 or in WO 2012/010560 A1 can be placed in different positions and alignments on a support surface in order to bring the transmit and receive antenna of the wireless mobile device close to an antenna structure of the circuit arrangement, wherein the antenna structure forms at least a part of a wireless signal coupling device. During the operation of the wireless mobile device, the transmission and reception signals (high-frequency signals for the operation in the mobile network) are transmitted wirelessly between the transmit and receive antenna of the wireless mobile device and the antenna structure. Due to the different positions and alignments, the signal damping caused by the wireless coupling differs, so that the additional signal damping also varies on the whole.